Microarraying and biological sensing are important emerging technologies with huge potential impact on clinical and research medicine. Present methodologies for microarraying and biological sensing are based on fluorescence, radioactive, colorimetry, or Surface Plasmon Resonance (“SPR”) assays of molecular recognition chemistry. To date, the former approach has garnered the most attention.
Although these methodologies work, there are problems with each of them. Fluorescence and radioactivity require a special tagging chemistry and, thus, are time-consuming and cumbersome to use. Additionally, methodologies based on radiation are hard to scale to arrays, and have associated safety and environmental problems. Colorimetry requires chemical amplification when there are large changes in the thickness of the coating and, thus, is very complicated to adapt to arraying.
Reflective interferometry (“RI”) has been demonstrated to be a powerful method for detection of adsorbate layers on surfaces. When combined with probes immobilized on a surface that are capable of selectively binding target biomolecules, RI can be used for sensitive detection of important pathogens and other applications. Experimental sensitivity to 2 Angstrom layers of adsorbates has been demonstrated and theoretical comparison with SPR predicts substantial improvements over the sensitivity of SPR if optimal geometries can be implemented. This is not surprising given the exquisite sensitivity of ellipsometric methods where the state-of-the-art is resolution in the picometer range.
The present invention is directed to overcoming these and other deficiencies in the art. The novel method of molecular sensing using Brewster angle straddle interferometry according to the present invention is capable of achieving suitably reproducible sensitivity at much lower cost using simpler equipment and less complex substrate design.